Amphibians, as every little kid knows, are born in water, as larvae, breathing water through gills. Later they undergo metamorphosis, and emerge from the water with (in most cases) air-breathing respiratory systems. Even after they’ve taken to land, though, they retain highly permeable skin that can act as a secondary breathing apparatus and aid them in oxygenating their blood underwater. They live just fine as broadly fish-like aquatic creatures for a while, and then just fine as broadly reptile-like terrestrial creatures for the rest of their lives. It’s very cool. Amphibians are very cool.

If you want to conceive of amphibians as reptiles plus the ability to breathe underwater, that’s basically fine. But it’d be much more accurate to think of them as reptiles minus the ability to be born outside of water or survive any real distance away from it. Amphibians basically are reptiles that failed to evolve the ability to lay eggs with impermeable membranes around them, and therefore must return to water to give birth ... to offspring burdened with the need to undergo a whole friggin’ biological overhaul just to live in the kind of environment where they will do pretty much all of their eating and mating. The highly permeable skin that gives amphibians some limited ability to hop back and forth from air to water without drowning in either medium actually makes them more vulnerable and specialized, not less: It loses moisture far more quickly than other types of skin, so amphibians must spend basically their entire lives in very damp conditions or shrivel up and die.

In the very narrowest, most immediate terms, amphibians are adaptable, in the sense that, say, a frog can toggle between breathing air on a lily pad in a muggy swamp and breathing water a few inches beneath that lily pad if circumstances require it to. But in every larger sense, between their permeable skin and their reproductive needs, amphibians are uncommonly specialized and vulnerable creatures. Their specific needs—constant damp, plus a nearby body of water for laying eggs in—make them highly sensitive to changes in the environment. Their population numbers decline in quick response to changes; they’ve been declining sharply for decades, in fact, in response to anthropogenic climate change. The things that make amphibians amphibians, ultimately, are sharp, debilitating disadvantages basically anywhere outside the conditions where amphibians live, and those conditions are narrow and fairly uncommon, globally speaking, and this is why there are not a lot of salamanders chilling out in the Alps.

What to do, then, if you are, say, a newspaper columnist and thinkfluencer, looking to classify what you view as an ascendant generation of millennials with, uh, “interesting backgrounds”—people of mixed race and social class, outsiders who have been forced by circumstance to “master two or three different ways of being in the world,” whose lives are “propelled by an electric, crosscutting cultural dynamic”? Under what label will you lump them into the sort of pseudo-sociological category (or, more practically speaking, voter focus-group demographic) that is your specialty? You want to characterize these people as hardy and adaptable, optimized survivors, “best suited to solve ... the big challenges of their generation.” Amphibia, a class of evolutionary relics uniquely unprepared to withstand a changing environment, will not do.

What, then? If you are committed to your idea of using taxonomy for this purpose, you might consider the taxonomic classes that best exemplify hardiness and adaptability. People might not like being classified as arthropods—who wants to be a cockroach?—but how about mammalia? With their self-regulating body temperatures, their ability to incubate their offspring inside themselves, and the warm fur that covers at least part of their bodies, mammals have shown the ability to thrive in virtually every corner of the global ecosystem.

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There are mammals everywhere! There are mammals in the frosty Himalayas: The snow leopard sometimes hunts for food as high as 18,000 feet of altitude, miles higher than any reptile could ever survive. There are mammals at the bottom of the ocean: The mighty sperm whale can stay submerged for up to 90 minutes—longer than some amphibians!—and endure water pressure strong enough to buckle the hull of a nuclear submarine. There are mammals in the driest desert: Saharan camels sometimes go months at a time getting water from nothing but the scant few plants they eat. There are mammals in Siberia, reindeer just walking around reasonably comfy in their thick fur in minus 90 degrees Fahrenheit like it is not even all that big a deal. Do you know what they call a frog in minus 90 degrees Fahrenheit? They call it ice. There are mammals in the buggy swamps and wet jungles amphibians call home: Beavers and bears and jaguars and frickin’ nutria, monkeys sometimes too. All of them generally doing better than the amphibians!

Well yes, you might say, but these animals are all specialized, too. I mean a sperm whale can’t just strut out of the water and hang out on land when it wants. This is true. In many ways the whale is an especially dumb creature: It breathes a whole different medium from the one it lives in. Its life is like if you had to go dip your toe in the ocean every hour or so in order to remain alive. Probably don’t call multiracial millennials sperm whales, then.

There are generalist mammals, though—specific mammals that live in basically every environment on earth. You can put one in a vessel and transport it from sunny New Zealand to friggin’ North Dakota and it will do just fine; ship more than one and they ought to have no trouble eating and reproducing wherever they wind up. They can (probably) even bang each other in outer space! No, I am not talking about rats here, please do not call these industrious heterogeneous youths rats. I am talking about humans! Just call them humans.

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(Of course then you’d have to drop the deeply dishonest pretense that there’s anything novel about brave, hardy, adaptable people of diverse, blended backgrounds migrating huge physical and social distances and bringing healthfully heterodox outlooks with them, and own up to the fact that the only new thing is a conservative white man deciding this is good rather than bad. Unfortunately for you, this blog is over!)